This invention relates to devices for immobilizing and sizing the human head when making panoramic radiographs of a portion of such head, for example, the full dental arch. More particularly, it is an improvement upon the device disclosed in U.S. Pat. No. 3,521,057 of A. F. Morlan, granted July 21, 1970, to which reference is hereby made, mainly regarding the purposes, application, and objectives of devices of this kind and their operative association with the chair and panoramic x-ray apparatus.